Silica-thickened grease containing carbamate salt as dispersant



SILICA-THICKENED GREASE CONTAINING CARBAMATE SALT AS DISPERSANT Nathaniel L. Remes, Elgin, and Thomas W. Martinek and Ernest T. Fronczak, Crystal Lake, 111., assignors to The Pure Oil Company, Chicago, 111., a corporation of Ohio No Drawing. Application April 24, 1957 Serial No. 654,638

' 10 Claims. (Cl. 252-28) This invention relates to new and useful improvements in grease composition and more particularly to a silicathickened grease utilizing an improved dispersant for the siilca gelling agent.

Although the classical definition of lubricating greases is restricted to oils which are thickened or gelled with soaps, there has been developed a number of grease-like lubricants which are based upon synthetic lubricating liquids other than oil, or which utilize gelling or thickening agents other than soaps, and are recognized as greases. In fact, non-soap-thickened greases have been given considerable attention in recent years for high temperature applications and are discussed at considerable length in the text Manufacture and Application of Lubricating Greases, Boner, Reinhold, 1954. The non-soap-thickened greases differ very substantially from the soap-thickened greases and differ among themselves to a very great extent. For example, the non-soap-thickened greases generally are less susceptible to bleeding and to change of consistency on increase of temperature. Bentone greases are thermally stable and highly resistant to water. On the other hand, silica-thickened greases are thermally stable but decompose readily in the presence of water unless water-proofing agents are used for the silica particles. Additives which are used for various purposes in connection with the soap-thickened greases are quite nited States Patent 2,913,409 Patented Nov. 17,v 1959 thickened greases, and a small amount of a hydrocarbon and having an average molecular weight of about 1400 variable in their effect on the various non-soap-thickened greases. For example, metal carbamates and thiocarbamates which are reported (in Patent 2,652,363) to be useful as corrosion inhibitors and stabilizers for soapthickened greases are completely ineffective as stabilizers for Bentone and silica-thickened greases. Butyl stearate and cocoanut oil are each reported (in Patent 2,662,058) to be useful as dispersion aids for Bentone greases but have been found to be completely ineffective as dispersants for silica-thickened greases. Similarly, the dispersants disclosed and claimed in this invention are useful for the preparation of silica-thickened greases but are ineffective in the preparation of Bentone greases. All of which tends to indicate the highly empirical nature of the grease-making art in general, and the art of making non-soap greases in particular.

It is therefore one object of this invention to provide a new and improved silica-thickened grease of high yield.

A feature of this invention is the provision of an improved silica-thickened grease using a hydrocarbon-substituted ammonium hydrocarbon-substituted carbamate, such as dimethylammoniumdimethylcarbamate, as a dispersant.

Other objects and features of this invention will become apparent from time to time throughout the specification and claims as hereinafter related.

This invention is based upon the discovery that silicathickened greases of very high yield can be prepared using hydrocarbon-substituted ammonium hydrocarbonsubstituted carbamates as dispersants for silica. When a silica-thickened grease is prepared utilizing standard grease-making techniques for the preparation of silica- (acetyl value). The mixture was thoroughly agitated and heated to l90-205 F. To this mixture there was added 7.0 parts by weight of finely-divided amorphous silica marketed under the trade name Cab-O-Sil. Cab-O-Sil is a finely-divided silica produced by high-temperature reaction of asiliceous material, e.g., high temperature, vapor-phase hydrolysisof silicon tetrachloride. The agitation of the mixture was continued during addition of the silica gelling agent and the mixture was agitated and maintained at 190-205 P. for a period of about 90 minutes. The material was then charged to a colloid mill with a rotor-stator clearance of 0.003 inch, and was milled at a flow rate of 0.6-0.7 lb. per minute. The grease thus produced was then allowed to cool and was tested using a standard cone penetration test. The grease had a worked penetration of 322, which is a NLGI #1 grease.

Example II To a conventional grease-processing kettle there was charged a mixture of 91.6 parts by weightof 160 vis. bright stock; a polyalkylene glycol, Ucon LB SSOX, 0.7 part by weight; and N,N-dimethylammoniumdirnethylcarbamate, 0.7 part by weight. The mixture was thoroughly agitated and heated to 190-205 F., and the agitation continued and temperature maintained constant during addition of the gelling agent and further processing of the grease. A finely-divided amorphous silica (Cab-O-Sil) 7.0 parts by weight, was added to the hot mixture in the kettle with continued agitation. The total mixture was agitated further for about 90 minutes while the temperature was maintained at 190205 F. The grease mixture was then charged to a colloid mill with a rotor-stator clearance of 0.003 inch and was milled at a flow rate of 0.6-0.7 lb. per minute. The grease thus produced was cooled and its consistency measured using the standard cone penetration test. This grease was found to have a worked penetration of 279, which corresponds to a NLGI #2 grease, a substantially higher yield grease than that produced in Example I.

In preparing greases according to this invention the silica gelling agent is added in an amount of 5-20% by weight of total composition. The substituted ammonium substituted carbamate is added in the amount of 2-15% of weight of the silica used, or 0.l-3.0% by weight of the total composition. The water-proofing agent, which may be used if desired, is added in the amount of 0.5-5.0%. The balance of the composition is the oleaginous lubricating liquid used as the base thereof. In formulating greases in accordance with this invention, it has been found that greases may be prepared which are thicker by increasing the amount of silica used or by using a greater proportion of the substituted ammonium substituted carbamate relative to the silica. In general, an increase in the carbamate-to-silica ratio increases the thickness or consistency of the grease for any given silica concentration therein.

3 Example III In still another experiment an attempt was made to use N,N-dimethylammoniumdimethylcarbamate as a dispersant for Bentone greases. In this experiment 90.1 parts by weight lubricating oil and 0.9 part by weight, N,N- dimethylammoniumdimethylcarbamate were charged to a grease-processing kettle, and agitated and heated as in the previous experiment. To this mixture there was added 9.0 parts by weight of finely-divided Bentone clay and the mixture processed in the same manner as the previous example. The product produced was completely fluid and was not a grease.

Example I V In still another experiment an attempt was made to prepare silica-thickened greases using zinc dibutyl dithiocarbamate as a dispersant for the silica. In this experiment 91.2 parts by weight of mineral oil and 0.8 part by weight zinc dibutyl dithiocarbamate were charged to a grease-processing kettle and heated and agitated as in Examples I and II. To this mixture there was added 8.0 parts by weight of finely-divided silica (Cab-O-Sil) and the mixture agitated, heated, and further processed as in Examples I and II. The product obtained in this process was completely fluid and was not a grease.

From these and other experiments it has been established that high-yield, silica-thickened greases can be prepared utilizing N,N-dimethylammoniumdimethyl carbamate as a dispersant for the silica. The hydrocarbonsubstituted ammonium hydrocarbon-substituted carbamates are generally useful as dispersants in the preparation of greases which comprise this invention. These carbamates have the general formula R R NCO NR R R R where R may be either hydrogen or hydrocarbon radicals and R R and R are hydrogen, or similar or dissimilar hydrocarbon radicals, which may be aryl, alkyl, aralkyl, or cycloalkyl in nature, and contain from 1 to 16 carbon atoms. useful are: N,N-dimethylammoniumdimethylcarbamate, N,N-dimethylammoniumdiethylcarbamate, N isopropylammoniumdimethylcarbamate, N phenylammoniurndimethylcarbamate, N benzylammoniumethylcarbamate. These carbamates are generally operative as dispersants for silica-thickened greases when added to the grease composition at a concentration of 215% of the weight of the silica. These substituted carbarnates are also useful as dispersants for silica in preparing greases from synthetic lubricants such as esters, polyethers, silicones and the like.

In formulating grease compositions according to this invention any oleaginous liquid can be used as the base for the grease and any finely-divided silica can be used as the gelling agent. Finely divided silica aerogels are useful for this purpose, although finely-divided amorphous silica produced by high-temperature, vapor-phase reaction or decomposition of siliceous compounds is preferred. Any eflective water-proofing agent, such as polyalkylene glycols, can be used to impart water resistance to the grease. Other additives may be used for their specific purposes as Examples of compounds of this class which are desired. As the dispersing agent, any hydrocarbon-substituted ammonium hydrocarbon-substituted carbamate of the general formula previously given can be used.

What is claimed is:

1. A lubricating grease comprising a major portion of an oleaginous lubricating liquid having incorporated therein sufiicient finely-divided silica to produce a gel-like grease structure and a carbamate of the formula where R R R and R are of the group consisting of hydrogen and hydrocarbon radicals containing 1-16 carbon atoms, at least one of the R groups-being a hydrocarbon radical, in an amount sufiicient to eflfect a complete dispersion of the silica.

2. A grease as defined in claim 1 which includes a waterproofing agent for the silica.

3. A grease as defined in claim 1 in which the carbamate is present in an amount of 215% of the silica.

4. A grease as defined in claim 3 in which the carbamate is N,N-dimethylammoniumdimethylcarbamate.

5. A lubricating grease comprising a major portion of a petroleum lubricating oil having incorporated therein sufficient finely-divided silica to produce a gel-like grease structure and a carbamate of a formula where R R R and R are of the group consisting of hydrogen and hydrocarbon radicals containing 1-16 carbon atoms, in an amount sufiicient to effect a complete dispersion of the silica.

6. A grease as defined in claim 5 which includes a water-proofing agent for the silica.

7. A grease as defined in claim 5 in which the carbamate is N,N-dimethylammoniurndimethylcarbamate. I 8. A grease as defined in claim 5 in which the silica used is an amorphous silica of very fine particle size produced by a high-temperature vapor-phase reaction of a siliceous material.

9. A lubricating grease comprising a major portion of a petroleum lubricating oil having incorporated therein 5-20% by weight of the total mixture of a gelling agent consisting of a very fine amorphous silica produced by a References Cited in the file of this patent UNITED STATES PATENTS 2,652,361 Woods et a1 Sept. 15, 1953 2,652,362 Woods et al Sept. 15, 1953 2,652,365 Moore Sept. 15, 1953 

1. A LUBRICATING GREASE COMPRISING A MAJOR PORTION OF AN OLEAGIOUS LUBRICATING LIQUID HAVING INCORPORATED THEREIN SUFFICIENT FINELY-DIVIDED SILICA TO PRODUCE A GEL-LIKE THEREIN SUFFICIENT FUNELY-DIVIDED SILICA TO PRODUCE A GEL-LIKE 